How to Talk to a Climate Skeptic: Responses to the most common skeptical arguments on global warming A Grist Special Series

'Global warming is nothing new'

Yes, the last ice age started thawing over 20,000 years ago, but that stopped a long time ago 5

(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: Global warming has been going on for the last 20,000 years.

Answer: It is true that 20,000 years ago the temperature was some 8 to 10° C colder than it is today. But to draw a line from that point to today and say, "look, 20K years of global warming!" is dubious and arbitrary at best.

If you have look at this graph of temperature, starting at a point when we were finishing the climb out of deep glaciation, you can clearly see that rapid warming ceased around 10,000 years ago (rapid relative to natural fluctuations, but not compared to the warming today, which is an order of magnitude faster). After a final little lift 8,000 years ago, temperature trended downward for the entire period of the Holocene. So the post-industrial revolution warming is the reversal of a many-thousand-year trend.

A closer look at today's trend, within the context of the last 1,000 and 2,000 years, makes it even clearer that today's trend is striking -- opposite to what one would expect without anthropogenic interference.

Reconstructed Temperature
(Courtesy of Global Warming Art. See source for details on the various reconstructions tangled above.)

If you really want to play the "global warming started X years ago" game, you should talk about how we're reversing a 5-million-year cooling trend -- or go crazy and track global temperatures right back to the origins of the planet! Not that there'd be much point ...

Former musician, turned tree planter, turned software engineer. Same old story…

I have been blogging about climate change since 2006 at A Few Things Ill Considered.

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  1. darudethedj Posted 1:40 am
    20 Feb 2007

    The mind of the skeptic

    An in depth article looking at why some "prominent figures" believe that man made global warming is a myth. It's important to know the enemy!

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  2. WWAGD?!'s avatar

    WWAGD?! Posted 2:08 am
    20 Feb 2007

    ChartJunk

    This is a good example of chart junk -- where the visuals overwhelm the data.   The link supporting that chart says:

    This image is a comparison of 10 different published reconstructions of mean temperature changes during the last 2000 years. More recent reconstructions are plotted towards the front and in redder colors, older reconstructions appear towards the back and in bluer colors. An instrumental history of temperature is also shown in black. The medieval warm period and little ice age are labeled at roughly the times when they are historically believed to occur, though it is still disputed whether these were truly global or only regional events. The single, unsmoothed annual value for 2004 is also shown for comparison. (Image:Instrumental Temperature Record.png shows how 2004 relates to other recent years).

    It is unknown which, if any, of these reconstructions is an accurate representation of climate history; however, these curves are a fair representation of the range of results appearing in the published scientific literature.

    So, first of all, it says that this chart may be inaccurate and yet, we're still going to run off and make policy decisions using it!

    Second, look at the scale.   Even the black line goes no higher than a 0.4C ( .5 to .7 degrees Fahrenheit ) anomaly.    All of the others fall within statistical range of the Medieval Warm Period.

    This chart shows clearly that global warming is naturogenic, not anthrogenic.

    The Texeme Construct offers international text memetics construction and textcasting services.

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  3. atreyger Posted 2:36 am
    20 Feb 2007

    umm, jabailo

    It's hard to extrapolate data from more than 100 years ago, when the records began to be kept. That's why there's uncertainty in the past. However, the range of uncertainty in the past is far below the certainty of the present both in terms of range and directionality: notice how the lines converge and all go up???

    Jeez, way to be a troll.

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  4. DaveR Posted 10:10 am
    28 Feb 2007

    I'm confused by your 8-10 degrees cooler comment

    On page 2 of the Jones/Mann report: "Climate Over Past Millennia (ftp://holocene.evsc.virginia.edu/pub/mann/JonesMannROG04.pdf), it states that at the last glacial maximum 21,000 years ago, global annual mean temperatures were about 4 degrees C colder than today. Why the discrepancy between your 8-10 degrees cooler figure and Jones/Mann's 4 degrees?

    Dave

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  5. Paul Wagner Posted 9:47 am
    18 Jun 2007

    Past Warming

    In the Pacific Northwest one finds Douglas-fir trees 600-800 years old at higher elevations than their natural range today.  They date from the medievel warm period.  In Alaska and in some of those Douglas-fir stands are found yellow cedars that are declining or dying because of early soil warming and late frosts.  Many of these trees date from the little ice age.

    Douglas-fir expanded its range when things were warmer and yellow cedar when it was colder.

    Evidence of past fluctuations and current change is very visible if you know what you are looking at.

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Series Intro
'There is no evidence' -- Yes, there is 59
'Mauna Loa is a volcano' -- CO2 rise is measured on top of a volcano! 8
'Warming is due to the Urban Heat Island effect' -- No, it isn't 25
'One hundred years is not enough'--Yes it is 18
'The scientists aren't even sure' -- No scientist ever is 33
'One record year is not global warming'--Luckily, there are plenty more years to consider 19
'Glaciers have always grown and receded'--A few glaciers melting does not mean global warming 14
'The temperature record is unreliable'--But temperature trends are clear and widely corroborated 8
'It's cold today in Wagga Wagga'--Weather and climate are different 2
'The satellites show cooling'--No, they don't 15
'What about mid-century cooling?'--No one said CO2 is the only climate influence 11
'Antarctic ice is growing'--Well, probably not, but even if it were, we are not off the hook 8
'Global warming stopped in 1998'--Only if you flagrantly cherry pick 170
'But the glaciers are not melting'--Except ... they are! 3
'Antarctic sea ice is increasing'--Yes, but ... 14
'Sea level in the Arctic is falling'--Sea level is a surprisingly complicated thing 11
'Climate sensitivity is not very high'--Thermal inertia of the oceans means the jury is still out 2
'Some sites show cooling'--But you can't draw global conclusions from individual sites 0
'Global warming is a hoax'--I wish James Inhofe were just a hoax ... 12
'There is no consensus'--If this is not consensus, what would consensus look like? 109
'Position statements hide debate'--True enough, but that is not the whole picture 5
'Consensus is collusion'--Is climate science maturing, or should we reach for our tinfoil hats? 8
'Peiser refuted Oreskes'--In a poor piece of work that has been retracted by its author 4
'Models don't account for clouds'--Clouds are complex and uncertain, but unlikely to stop warming 6
'Climate models are unproven'--Actually, GCM's have many confirmed successes under their belts 13
'Aerosols should mean more warming in the south'--More North. Hemisphere warming is well-understood 1
'We can't even predict the weather next week'--But weather is not climate 11
'Chaotic systems are not predictable'--Sure, but who says climate is chaotic? 13
Understanding what is happening right under our noses does not require paleoclimate perfection 1
'They predicted global cooling in the 70s'--But that didn't even remotely resemble today's consensus 29
'Hansen has been wrong before'--Maybe, but not about the climate! 13
'It was warmer during the Holocene Climatic Optimum'--This period was not global and not like today 4
'The Medieval Warm Period was just as warm as today'--Repeating this point does not make it true 216
'Greenland used to be green'--Don't judge a book by its cover, much less a land by its name 23
Yes, the last ice age started thawing over 20,000 years ago, but that stopped a long time ago 5
'The hockey stick is broken'--Well, no ... but who's playing hockey anyway? 6
'Vineland was full of grapes'--Or was it an early advertising campaign? 4
'Global warming is part of a natural cycle'--This idea is one short step above appealing to magic 39
'Mars and Pluto are warming too'--No they aren't -- and what if they were? 24
'Volcanoes emit more CO2 than humans'--Not even close ... 31
'The null hypothesis says warming is natural'--An inappropriate test, and one that would fail anyway 4
'Climate is always changing'--That doesn't mean it isn't different today 5
'Natural emissions dwarf human emissions'--But emissions are only one side of the equation 5
'The CO2 rise is natural'--No skeptical argument has been more definitively disproven 12
'We are just recovering from the LIA'--Why should we expect this to happen? 4
'Climate scientists dodge the subject of water vapor'--No, they really don't 4
Water vapor is indeed a powerful greenhouse gas, but there is plenty of room for CO2 to play a role 29
There is no proof in science, but there are mountains of evidence 78
'CO2 doesn't lead, it lags'--Turns out CO2 rise is both a cause and an effect of warming 43
'Geological history does not support CO2's importance'--Just not true 0
'Historically, CO2 never caused temperature change'--Not so 19
'It's the sun, stupid'--Very bright, yes, but not getting brighter 18
The problem is not how high the temperature may go, but how fast it is changing 14
'Kyoto is a big effort for almost nothing'--Kyoto is only in its first phase 16
China and India have joined Kyoto, they just have different obligations, as is morally appropriate 3
'Climate change mitigation would lead to disaster'--Not really, but this may be lesser of two evils 6
Only if you ignore fossil fuel emissions 10
In 2008, did temperatures drop as much as they rose over the whole 20th century? 71
Is the IPCC so wrong their theories contradict a basic laws of physics? 23
Is the American Physical Society a crack in the climate change consensus? 3
Summer ice in the Arctic has recovered--Was the Arctic ice retreat a climate anomaly? 7
'Global warming comes from within'--Is heat at the Earth's core the real cause of global warming? 10
Was there another breathless announcement of another phony record, and another quiet retraction? 1
Hansen wants the skeptics thrown in jail--Did James Hansen really want to try the climate skeptics? 6
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